there are many threads on gettign ESX and ESXi to work under Workstation, just do a search.
but the basic crux is that, if you can get it to work, unless your Host machine is very powerfull and dedicated to the job the overhead that virtualisation over virtualistion puts on the end machine is such that for anything other than demo, it is next to useless. ie real work is a no-no.
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Tom Howarth VCP / VCAP / vExpert VMware Communities User Moderator Blog: http://www.planetvm.net Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410